A light emitting module on an illuminated keyboard usually consists of a flexible printed circuit (FPC) board and a light emitting diode (LED), and is disposed at one side of the keyboard to radiate light toward the other side, so that light is radiated from below keys of the keyboard, and users can see the keys at night or when there is insufficient light.
Normally, keyboards are of rectangular shape and are elongated in a lateral dimension. Therefore, a light emitting module is usually disposed at an upper side or a lower side of the keyboard, so light can be projected in a vertical direction to obtain uniform illumination. However, this configuration raises a cost in an FPC material. Although the cost in the FPC material can be reduced by disposing the light emitting module in the middle in order to project light laterally to left and right sides, the light emitting diodes (LEDs) are disposed too centralized, so an overheating problem may occur. Moreover, since the keyboard is longer in the lateral dimension, a light path is longer in the lateral dimension, and it is difficult to achieve uniform illumination (light intensity is not uniform because the light intensity decreases as the distance increases).
Accordingly, the inventor made various studies to overcome the above-mentioned problems, on the basis of which the present invention is accomplished.